So this is all kind of complicated...
I'm dating this guy, who I had a short-lived thing with sophomore year (we are now seniors) and after our thing sophomore year ended we stayed really close friends, saw other people, but always had something for eachother. People have described it as us being meant for eachother, just searching for the right time.
This summer, when I came back from being abroad, we started hooking up again, keeping it casual and not really defining what our relationship was. This fall, we continued hooking up, and started to talk about what we wanted to do. I told him that I didn't want to tie him down or anything (because he had never been in an actual boyfriend-girlfriend relationship), so I was okay if he wanted to see other people, but he told me I was the only girl he wanted to be with etc etc. We weren't together or anything at the time, but it was just something we were both considering.
I also knew that another girl, who lives right down the hall from me, had her eye on him, and that they had made out once before, but she had a boyfriend. I asked him straight up front, because we had always been somewhat upfront about our relationships, if they were hooking up and having sex. I thought I deserved to know this because he and I were sexually involved at the time. He told me yes they had hooked up once (we can call this girl girl A), but never had sex. So I was done with it.
A few weeks later, we finally decided to go to the next step of being "together" whatever that means. We decided to only hook up with eachother. The NIGHT after we decided this, he got drunk and made out with his most recent ex-hookup. He never told me about it, I found out a few weeks later, confronted him about it and considered ending it, but didn't because it seemed so out of his character. He promised that he had "no secrets" anymore and I trusted him.
The other day I found out that he had had sex with girl A, and had lied to me about it, while we were having sex. I confronted him, and he lied again that it happened. When I made it clear that I knew he was lying, he said it only happened once. Then I questioned him...and he said it had happened twice. The next day when we were talking about it, he said it happened three times.
I don't really know what to do. I know its not my business what he did while he was technically single, but it is still kind of shitty that he was having sex with another girl while having sex with me. What I'm really bothered about is the LYING and then the covering up of the lying.